L A Bracero1,2, C Huff1, M J Blitz3, M J Plata4, D J Seybold5, M Broce5. 1. Department of Obstetrics and Gynecology, West Virginia University Charleston Campus, Charleston, WV, USA. 2. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Hofstra Northwell School of Medicine, Southside Hospital, Bay Shore, NY, USA. 3. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Hofstra Northwell School of Medicine, North Shore University Hospital, Manhasset, NY, USA. 4. Department of Pathology, Charleston Area Medical Center, Charleston, WV, USA. 5. Center for Health Services & Outcomes Research, Charleston Area Medical Center, Charleston, WV, USA.
Abstract
OBJECTIVE: To determine how prenatal ultrasound measurements of dividing membrane thickness correlate with postnatal histological measurements and chorionicity in twin gestations. METHODS: This was a prospective, longitudinal cohort study of twin gestations. Dividing membrane thickness was measured by transabdominal ultrasound, with the insonation beam both parallel and perpendicular to the membrane, in the second or third trimester, depending on when care was established. Ultrasound examinations were performed every 4 weeks following initial assessment until delivery. Measurements of membrane thickness from the first ultrasound examination were compared with histological measurements after delivery. RESULTS: A total of 45 twin pregnancies (32 dichorionic, 13 monochorionic) were included. Mean gestational age at initial ultrasound examination was 24.1 ± 7.3 weeks. Parallel ultrasound measurements of membrane thickness were 1.6 ± 0.8 mm for monochorionic and 2.5 ± 0.9 mm for dichorionic gestations (P = 0.001). Perpendicular ultrasound measurements were 1.6 ± 0.3 mm for monochorionic and 2.2 ± 0.8 mm for dichorionic gestations (P = 0.009). Inter- and intraobserver reliability of ultrasound measurements were 0.847 and 0.950, respectively. Parallel and perpendicular ultrasound measurements correlated better with each other (R = 0.807, P < 0.001) than with histological measurements of membrane thickness (Rparallel = 0.538, P < 0.001; Rperpendicular = 0.529, P < 0.001). Receiver-operating characteristics curve analyses to predict histological membrane thickness > 50th percentile resulted in an area under the curve (AUC) of 0.828 for parallel (P < 0.001) and 0.874 for perpendicular (P < 0.001) measurements with a cut-off value of 1.9 mm for both approaches. The AUCs for parallel and perpendicular measurements to predict dichorionicity were 0.892 (P < 0.001) and 0.823 (P < 0.001) with cut-off values of 1.9 and 1.8 mm, respectively. CONCLUSION: Prenatal ultrasound measurement of twin dividing membrane thickness is positively correlated with postnatal histological measurement. Dichorionicity can be determined by a magnified dividing membrane thickness ≥ 1.9 mm. Measurements with the ultrasound beam parallel to the dividing membrane may be more accurate than perpendicular measurements.
OBJECTIVE: To determine how prenatal ultrasound measurements of dividing membrane thickness correlate with postnatal histological measurements and chorionicity in twin gestations. METHODS: This was a prospective, longitudinal cohort study of twin gestations. Dividing membrane thickness was measured by transabdominal ultrasound, with the insonation beam both parallel and perpendicular to the membrane, in the second or third trimester, depending on when care was established. Ultrasound examinations were performed every 4 weeks following initial assessment until delivery. Measurements of membrane thickness from the first ultrasound examination were compared with histological measurements after delivery. RESULTS: A total of 45 twin pregnancies (32 dichorionic, 13 monochorionic) were included. Mean gestational age at initial ultrasound examination was 24.1 ± 7.3 weeks. Parallel ultrasound measurements of membrane thickness were 1.6 ± 0.8 mm for monochorionic and 2.5 ± 0.9 mm for dichorionic gestations (P = 0.001). Perpendicular ultrasound measurements were 1.6 ± 0.3 mm for monochorionic and 2.2 ± 0.8 mm for dichorionic gestations (P = 0.009). Inter- and intraobserver reliability of ultrasound measurements were 0.847 and 0.950, respectively. Parallel and perpendicular ultrasound measurements correlated better with each other (R = 0.807, P < 0.001) than with histological measurements of membrane thickness (Rparallel = 0.538, P < 0.001; Rperpendicular = 0.529, P < 0.001). Receiver-operating characteristics curve analyses to predict histological membrane thickness > 50th percentile resulted in an area under the curve (AUC) of 0.828 for parallel (P < 0.001) and 0.874 for perpendicular (P < 0.001) measurements with a cut-off value of 1.9 mm for both approaches. The AUCs for parallel and perpendicular measurements to predict dichorionicity were 0.892 (P < 0.001) and 0.823 (P < 0.001) with cut-off values of 1.9 and 1.8 mm, respectively. CONCLUSION: Prenatal ultrasound measurement of twin dividing membrane thickness is positively correlated with postnatal histological measurement. Dichorionicity can be determined by a magnified dividing membrane thickness ≥ 1.9 mm. Measurements with the ultrasound beam parallel to the dividing membrane may be more accurate than perpendicular measurements.